1. Field
Various features pertain to wireless communication systems. At least one aspect pertains to methods for mobile time and frequency tracking and compensation at a wireless communication device.
2. Background
Wireless communication systems are widely deployed to provide various types of communication contents, such as, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications, such as, third generation partnership project (3GPP), 3GPP, long-term evolution (LTE), etc.
Generally, wireless multiple-access communication systems may simultaneously support communication for multiple access terminals (e.g., mobile devices). Each access terminal may communicate with one or more access points via transmissions on forward and reverse links. The forward link (FL or downlink) refers to the communication link from the access points to access terminals, and the reverse link (RL or uplink) refers to the communication link from the access terminals to access points. Further communications between access terminals and access points may be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems and so forth. In addition, access terminals may be capable of communicating with other access terminals (and/or access points with other access points) in peer-to-peer wireless network configurations.
Time and frequency synchronization is fundamental to performance of any mobile wireless communication system. Mobile access terminal (e.g., mobile device) clock drift and movement are two major contributors affecting mobile time and frequency synchronization. Time and frequency tracking, based on a forward link signal arriving at the mobile access terminal and a reverse link signal arriving at the access point separately, cannot differentiate between effects from mobile clock drift versus mobile movement and therefore cannot achieve the best possible synchronization. Mobile access terminal performance is thus compromised, especially when mobile access terminal movement is not negligible. Also, if a feedback-based correction scheme is utilized based on feedback from the access point, such scheme adds undesirable signaling overhead to the wireless system.
Consequently, a method is needed to improve performance of the mobile access terminal by differentiating between the effects of mobile clock drift and movement, and to lessen signaling overhead between the mobile access terminal and an access point.